1. Field of the Invention
In this specification, a semiconductor device, a method for driving the semiconductor device, and a method for manufacturing the semiconductor device are described.
Note that in this specification, a semiconductor device means a circuit including a semiconductor element (e.g., a transistor or a diode). The semiconductor device also means any device that can function by utilizing semiconductor characteristics. For example, an integrated circuit, a chip including an integrated circuit, a display device, a light-emitting device, and an electronic device are all semiconductor devices.
2. Description of the Related Art
A programmable logic device (PLD) is a kind of large integrated circuit (LSI), and is an integrated circuit whose internal circuit structure can be changed by a user with programming after shipment.
Fundamental components of the PLD are a plurality of logic elements that execute logical operation and wirings that connect the logic elements to each other. The function of the PLD is changed by changing the function of each logic element and connection between the logic elements.
For example, a programmable switch circuit in which a path transistor is combined with a memory storing data for setting the on or off state of the path transistor is known as a switch that connects logic elements to each other. By rewriting data for setting the on or off state of the path transistor, connection between the logic elements can be changed.
Data for setting the structure of the PLD is referred to as configuration data. A memory storing configuration data is referred to as a configuration memory.
In addition, it is known that a transistor including an oxide semiconductor has extremely low off-state current. For example, Patent Documents 1 and 2 disclose programmable switches each formed using a transistor including an oxide semiconductor. By using the transistor including an oxide semiconductor, unlike a DRAM, the gate potential of a path transistor can be held for a long period without refresh operation.